Capacitor structure

ABSTRACT

A capacitor structure has a plurality of stacked conductive patterns, and each conductive pattern has a closed conductive ring, a plurality of major conductive bars arranged in parallel and electrically to the closed conductive ring, and a plurality of minor conductive bars arranged alternately with the major conductive bars and not electrically connected to the closed conductive ring. The major conductive bars and the minor conductive bars of an odd layer conductive pattern are respectively corresponding to the minor conductive bars and the major conductive bars of an even layer conductive pattern.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a capacitor structure, and moreparticularly, to a capacitor structure with high capacitance and highmatching.

2. Description of the Prior Art

Capacitor, device for storing charges, is normally adopted in variousICs e.g. RFIC and analog circuit. Basically, a capacitor structureincludes two parallel electrode plates and an insulator disposed inbetween the electrode plates. With reference to FIG. 1, FIG. 1 is aschematic diagram of a conventional flat plate capacitor structure. Asshown in FIG. 1, the flat plate capacitor 10 includes a substrate 12, afirst electrode plate 14 disposed on the substrate 12, a capacitordielectric layer 16 disposed on the first electrode plate 14, and asecond electrode plate 18 disposed on the capacitor dielectric layer 16.

However, the first electrode plate 14, the capacitor dielectric layer16, and the second electrode plate 18 are stacked up horizontally, andtherefore the increase of overlapping region will result in reduction ofintegration.

U.S. Pat. No. 5,583,359 discloses an interdigitated capacitor structure.With reference to FIG. 2 and FIG. 3, FIG. 2 is an oblique schematicdiagram of a conventional interdigitated capacitor structure 30, andFIG. 3 is a cross-sectional view of the interdigitated capacitorstructure 30 along a tangent line III-III. As shown in FIG. 2 and FIG.3, the interdigitated capacitor structure 30 includes a first electrodestructure and a second electrode structure. The first electrodestructure includes a plurality of vertically stacked first conductivepatterns 32, and the second electrode structure includes a plurality ofsecond conductive patterns 34. Each first conductive pattern 32 has afirst peripheral conductive bar 321 and a plurality of first conductivefingers 322, and each second conductive pattern 34 has a secondperipheral conductive bar 341 and a plurality of second conductivefingers 342. The interdigitated capacitor structure 30 further includesa capacitor dielectric layer 38 (not shown in FIG. 2) disposed inbetween the first conductive patterns 32 and the second conductivepatterns 34, a plurality of first contact plugs 40 disposed in thecapacitor dielectric layer 38 between the first peripheral conductivebars 321, and a plurality of second contact plugs 42 disposed in thecapacitor dielectric layer 38 between the second peripheral conductivebars 341.

As shown in FIG. 2, the first conductive patterns 32 are connectedtogether with the first contact plugs 40, and the second conductivepatterns 34 are connected together with the second contact plugs 42.Therefore, the first conductive patterns 32, the second conductivepatterns 34, and the capacitor dielectric layer 38 constitute theconventional interdigitated capacitor structure 30. As shown in FIG. 3,the first conductive fingers 322 are applied with positive voltage,while the second conductive fingers 342 are applied with negativevoltage.

In comparison with the flat plate capacitor structure, the conventionalinterdigitated capacitor structure has higher capacitance. However, theconductive patterns are electrically connected to each other with thecontact plugs disposed in the dielectric layer between the peripheralconductive bars, and therefore the capacitance can be improved.

SUMMARY OF THE INVENTION

It is therefore one object of the claimed invention to provide acapacitor structure with high capacitance and matching.

According to the claimed invention, a capacitor structure is provided.The capacitor structure includes a first layer conductive pattern, asecond layer conductive pattern disposed above the first layerconductive pattern, a dielectric layer sandwiched between the firstlayer conductive pattern and the second layer conductive pattern, and aplurality of contact plugs disposed in the dielectric layer forelectrically connecting the first layer conductive pattern and thesecond layer conductive pattern. The first layer conductive patternincludes a first closed conductive ring, a plurality of first majorconductive bars arranged in parallel and electrically connected to thefirst closed conductive ring, and a plurality of first minor conductivebars arranged alternately with the first major conductive bars and notelectrically connected to the first closed conductive ring. The secondlayer conductive pattern includes a second closed conductive ring, aplurality of second major conductive bars arranged in parallel andelectrically connected to the second closed conductive ring, and aplurality of second minor conductive bars arranged alternately with thesecond major conductive bars and not electrically connected to thesecond closed conductive ring. The first major conductive bars areelectrically connected to the second minor conductive bars, and thesecond major conductive bars are electrically connected to the firstminor conductive bars.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a conventional flat plate capacitorstructure.

FIG. 2 is an oblique schematic diagram of a conventional interdigitatedcapacitor structure.

FIG. 3 is a cross-sectional view of the interdigitated capacitorstructure along a tangent line III-III.

FIG. 4 schematically illustrates a layout pattern of a first layerconductive pattern.

FIG. 5 schematically illustrates a layout pattern of a second layerconductive pattern.

FIG. 6 is an oblique schematic diagram of a capacitor structure inaccordance with a preferred embodiment.

FIG. 7 is a cross-sectional view of the capacitor structure shown inFIG. 6 along a tangent line VII-VII.

DETAILED DESCRIPTION

Please reference to FIG. 4 and FIG. 5. FIG. 4 schematically illustratesa layout pattern of a first layer conductive pattern 50, and FIG. 5schematically illustrates a layout pattern of a second layer conductivepattern 60 in accordance with a preferred embodiment of a capacitorstructure. It is appreciated that the capacitor structure of the presentinvention is not limited to a two-layer structure, and can be amulti-layer structure. For a multi-layer structure, the layout patternof a conductive pattern of an odd layer is identical to the first layerconductive pattern 50, and the layout pattern of a conductive pattern ofan even layer is identical to the second layer conductive pattern 60. Asshown in FIG. 4, the first layer conductive pattern 50 includes a firstclosed conductive ring 52, a plurality of first major conductive bars 54arranged in parallel and electrically connected to the first closedconductive ring 52, and a plurality of first minor conductive bars 56arranged alternately with the first major conductive bars 54 and notelectrically connected to the first closed conductive ring 52. As shownin FIG. 5, the second layer conductive pattern 60 includes a secondclosed conductive ring 62, a plurality of second major conductive bars64 arranged in parallel and electrically connected to the second closedconductive ring 62, and a plurality of second minor conductive bars 66arranged alternately with the second major conductive bars 64 and notelectrically connected to the second closed conductive ring 62.

The capacitor structure of the present invention is fabricated bystacking the first layer conductive pattern 50 and the second layerconductive pattern 60. The first closed conductive ring 52, the firstmajor conductive bars 54, and the first minor conductive bars 56 arerespectively corresponding to the second closed conductive ring 62, thesecond minor conductive bars 66, and the second major conductive bars64. In addition, the capacitor structure further has a dielectric layer(not shown) sandwiched between the first layer conductive pattern 50 andthe second layer conductive pattern 60, and a plurality of contact plugs70 formed in between the dielectric layer to electrically connect thefirst major conductive bars 54 and the second minor conductive bars 66,and to connect the second major conductive bars 64 and the first minorconductive bars 56 as well. Furthermore, each of the first layerconductive pattern 50 and the second layer conductive pattern 60 has anI/O port for external connections.

One of the main features of the capacitor structure of the presentinvention is that each of the closed conductive ring, the majorconductive bar, and the minor conductive bar has a symmetric shape, sothat the matching of the capacitor structure is improved. As shown inFIG. 4 and FIG. 5, the first closed conductive ring 52 and the secondclosed conductive ring 62 are rectangular, and the first majorconductive bar 54, the first minor conductive bar 56, the second majorconductive bar 64, and the second minor conductive bar 66 are strippedin this embodiment. However, the present invention is not limited by theabove embodiment, and these components can be modified to any symmetricshapes wherever necessary.

Please refer to FIG. 6 and FIG. 7. FIG. 6 is an oblique schematicdiagram of a capacitor structure in accordance with a preferredembodiment, and FIG. 7 is a cross-sectional view of the capacitorstructure shown in FIG. 6 along a tangent line VII-VII. In thisembodiment, a four-layer capacitor structure is illustrated. As shown inFIG. 6 and FIG. 7, the capacitor structure includes a plurality ofstacked conductive patterns, where the pattern layouts of the conductivepatterns of odd layers (i.e. the first layer and the third layer) 80 areidentical to the pattern layout of the first layer conductive pattern 50(shown in FIG. 4), and the pattern layouts of the conductive patterns ofeven layers (i.e. the second layer and the fourth layer) 90 areidentical to the pattern layout of the second layer conductive pattern60 (shown in FIG. 5). The capacitor structure has a dielectric layer 100sandwiched between the conductive patterns 80 and 90, and a plurality ofcontact plugs disposed in the dielectric layer 100 for connecting theconductive patterns 80 and 90. The contact plugs 72 are used toelectrically connect the major conductive bars of the conductive pattern80 to the minor conductive bars of the conductive pattern 90, and thecontact plugs 74 are used to electrically connect the major conductivebars of the conductive pattern 90 to the minor conductive bars of theconductive pattern 80. It is appreciated that the contact plugs 72 and74 are used to couple the conductive patterns 80 and 90. Thus the shape,size, and arrangement density of the contact plugs 72 and 74 are notlimited by the configuration illustrated in FIG. 6 and FIG. 7, and canbe modified to obtain an optimal capacitance and matching. In addition,fabrication of the capacitor structure of the present invention can beintegrated into the metal interconnection process. In such a case, theconductive pattern can be metal material e.g. aluminum or copper, butthe conductive pattern can also be any conductive materials such aspolycrystalline silicon. The material of the contact plugs can betungsten, copper, aluminum, etc. The dielectric layer may be siliconoxide, silicon nitride, silicon oxynitride, or any single or compositedielectric materials.

The capacitor structure has good matching because of the symmetriclayout. In addition, the capacitance of the capacitor is contributed bythe vertical capacitance between the conductive patterns, the horizontalcapacitance between the major conductive bars and the minor conductivebars of each conductive pattern, and the horizontal capacitance betweenthe contact plugs, and therefore the unit capacitance of the capacitorstructure can be improved.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

1: A capacitor structure, comprising: a first layer conductive patterncomprising: a first closed conductive ring; a plurality of first majorconductive bars arranged in parallel and electrically connected to thefirst closed conductive ring; and a plurality of first minor conductivebars arranged alternately with the first major conductive bars and notelectrically connected to the first closed conductive ring; a secondlayer conductive pattern disposed above the first layer conductivepattern, the second layer conductive pattern comprising: a second closedconductive ring; a plurality of second major conductive bars arranged inparallel and electrically connected to the second closed conductivering; and a plurality of second minor conductive bars arrangedalternately with the second major conductive bars and not electricallyconnected to the second closed conductive ring; a dielectric layersandwiched between the first layer conductive pattern and the secondlayer conductive pattern; and a plurality of contact plugs disposed inthe dielectric layer, comprising a plurality of first contact plugs anda plurality of second contact plugs, wherein each of the first minorconductive bars is electrically connected to the second major conductivebars through at least two of the first contact plugs, and each of thesecond minor conductive bars is electrically connected to the firstmajor conductive bars through at least two of the second contact plugs.2: The capacitor structure of claim 1, wherein each of the first closedconductive ring and the second closed conductive ring has a symmetricshape. 3: The capacitor structure of claim 1, wherein each of the firstmajor conductive bars and the second major conductive bars has asymmetric shape. 4: The capacitor of claim 1, wherein each of the firstminor conductive bars and the second minor conductive bars has asymmetric shape. 5: The capacitor structure of claim 1, wherein thefirst layer conductive pattern and the second layer conductive patterncomprise metal or polycrystalline silicon. 6: The capacitor structure ofclaim 1, wherein the dielectric layer comprises silicon oxide, siliconnitride, or silicon oxynitride. 7: The capacitor structure of claim 1,wherein a capacitance of the capacitor structure is contributed by avertical capacitance between the first layer conductive pattern and thesecond layer conductive pattern, a horizontal capacitance between thefirst major conductive bars and the first minor conductive burs, ahorizontal capacitance between the second major conductive bars and thesecond minor conductive bars, and a horizontal capacitance between thecontact plugs. 8: The capacitor structure of claim 1, further comprisinga third layer conductive pattern and a fourth layer conductiverespectively stacked above the second layer conductive pattern, thethird layer conductive pattern and the first layer conductive patternhaving same pattern layouts, and the fourth layer conductive pattern andthe second layer conductive pattern having same pattern layouts. 9: Acapacitor structure, comprising: a plurality of stacked conductivepatterns, each conductive pattern comprising a closed conductive ring, aplurality of major conductive bars arranged in parallel and electricallyconnected to the closed conductive ring, and a plurality of minorconductive bars arranged alternately with the major conductive bars andnot electrically connected to the closed conductive ring, wherein themajor conductive bars and the minor conductive bars of the conductivepattern of an odd layer are corresponding to the minor conductive barsand the major conductive bars of the conductive pattern of an evenlayer, and each of the minor conductive bars is longer than its width;at least a dielectric layer disposed between the conductive patterns;and a plurality of contact plugs disposed in the dielectric layer,wherein the major conductive bars and the minor conductive bars of theconductive pattern of the odd layer are electrically connected to theminor conductive bars and the major conductive bars of the conductivepattern of the even layer with the contact plugs. 10: The capacitorstructure of claim 9, wherein each closed conductive ring has asymmetric shape. 11: The capacitor structure of claim 9, wherein eachmajor conductive bar has a symmetric shape. 12: The capacitor structureof claim 9, wherein each minor conductive bar has a symmetric shape. 13:The capacitor stricture of claim 9, wherein each conductive patterncomprises metal. 14: The capacitor structure of claim 9, wherein eachconductive pattern comprises polycrystalline silicon. 15: The capacitorstructure of claim 9, wherein the dielectric layer comprises siliconoxide, silicon nitride, and silicon oxynitride. 16: The capacitorstructure of claim 9, wherein a capacitance of the capacitor structureis contributed by a vertical capacitance between the conductivepatterns, a horizontal capacitance between the major conductive bars andthe minor conductive bars of each conductive pattern, and a horizontalcapacitance between the contact plugs.